1. Field of the Invention
This invention relates to magnetic tape cassettes, and in particular, to a tape cassette encasing therein a feed reel on which magnetic tape is wound and a take-up reel.
2. Description of the Prior Art
With the recent development of small and light-weight cassette tape recorders, the cassettes for tapes used therein are miniaturized, and further it is highly desirable that the tape in the cassette is capable of providing high density recording and reproduction for a long period of time. Tapes which fulfill the need as noted above include tapes such as the so-called C-120, C-180 and the like, which have been put to practical use. It is also required that the surface of the recording medium have a mirror-like finish to provide high density recording and reproduction.
In the past, tapes with surfaces finished as previously mentioned and which are very thin have been set within a tape cassette as shown in FIGS. 1 and 2.
The cassette 1 comprises an upper case 2 and a lower case 3, which are integrally fastened by fastner members 4 to form a hollow interior which is divided into a recording and reproduction area 6 and a reel receiving area 7 by a partition member 5 formed to project from inner surfaces of the upper and lower cases 2 and 3, respectively. The reel receiving area 7 includes a pair of reels 8, 9, flanged rotary guide rollers 11, 11', fixed pins 10, 10' arranged in symmetrical fashion relative to a center line C, and cushion sheets 13 disposed between the inner surfaces of the upper and lower cases 2, 3 and sides of the reels 8, 9.
The recording and reproduction area 6 includes a pressure means 12 for pressing an antimagnetism surface of tape T, and the upper and lower cases 2, 3 defining the recording and reproduction area 6 have a plurality of openings 14 at the sides thereof.
The tape T, one end of which engages the reel 8 while the other end engages the reel 9, passes along a tape travel path 15, which comprises fixed pin 10, flanged rotary guide roller 11, pressure means 12, flanged rotary guide roller 11', and fixed pin 10'. The position of the tape in the direction of the width thereof is constantly being corrected by the cushion sheets 13 which are preferably embossed and have a low coefficient of friction.
It should be noted that the flanged rotary guide rollers 11, 11' also have the function of correcting the position of the tape in of the width direction, similarly to that of the cushion sheets 13, when the tape T travels, but the fixed pins 10, 10' only serve to carry the tape T by the outer peripheral surfaces thereof.
Further, the upper and lower cases 2, 3 have been formed flat; except for the portions which the fastner members 4 extend through.
However, the well-known tape cassettes as previously mentioned have the following disadvantages:
(1) The repetition of quick feeding and unreeling operations and low speed recording and reproduction operations causes a rapid shift between low speed sliding contact status of the tape and a high speed sliding status of the tape at the outer peripheral surfaces of the fixed pins 10, 10'. As a consequence the tape tends to move to the upper and lower parts of the pins. In addition, if cores of the fixed pins 10, 10' or the outer peripheral surfaces thereof are not exactly parallel to each other and to the surface of the tape T, a steep variations in tension result thereby biasing the tape T in the width direction to accelerate an unbalanced stress. As a consequence creases, uneven elongation at one edge, scratches, etc. are induced in the surface of the tape to materially render the reproduction output unstable.
(2) If a strain is produced when the upper and lower cases 2 and 3 are assembled, the reels 8, 9 supported on the upper and lower cases 2, 3, the fixed pins 10, 10' and the flanged rotary guide rollers 11, 11' tend to be out of alignment, resulting in an increase of travelling, particularly, biasing in the width direction of the tape T.